China 
Africa 
Explore chapters and articles related to this topic
Risks, Toxicity, and Challenges of Nanomaterials
Published in Rajendra Kumar Goyal, Nanomaterials and Nanocomposites, 2017
Silver may be released into the air and water through natural processes such as weathering of rocks or by human activities. Rain may wash silver out of soil into the groundwater. Silver can be present in four different oxidation states: Ag0, Ag+, Ag2+, and Ag3+. The former two are the most abundant ones; the latter two are unstable in the aquatic environment. The free silver ion is Ag+. In the environment, silver is found as a monovalent ion together with sulfide, bicarbonate, sulfate, or more complex forms with chlorides and sulfates adsorbed onto particulate matter in the aqueous phase. Metallic silver itself is insoluble in water, but metallic salts such as silver nitrate (AgNO3) and silver chloride (AgCl) are readily soluble in water. Metallic silver appears to pose minimal risk to health, whereas soluble silver compounds are more readily absorbed and produce adverse effects. The acute toxicity of silver is dependent on its chemical form and the availability of free silver ions. For an aqueous concentration of only 1–5 mg/L, sensitive aquatic organisms and insects, trout, and flounder can be killed. Furthermore, accumulation of silver in species exposed to a slightly lower concentration of silver has led to adverse effects on growth. Silver is usually not available in concentrations high enough to pose a risk to human health and the environment. If nanosilver is in large concentration, then it could pose a threat to human health and environment. Nanosilver is also used in washing machines because of its antimicrobial activity; however, wastewater containing silver ions is drained into the ecosystem. This may affect the beneficial bacteria in soil, which are essential for the soil used for farming. The addition of silver NPs to socks kills the bacteria associated with foot odor. Unfortunately, the silver may easily leak into wastewater during two to four washings depending upon the manufacturers of the socks. Thus, these silver NPs disturb helpful bacteria used in wastewater treatment facilities or endanger aquatic organisms in lakes and streams. Such incidents have raised the concern of governments and the public. There are Ag-resistant bacteria in our mouths, which may be possibly related to the Ag in amalgam fillings. Ag-resistant bacteria have also been found in nature, food, and intestinal bacteria from different geographic locations and hospitals [1,2].
Insights into footwear preferences and insole design to improve thermal environment of footwear
Published in International Journal of Fashion Design, Technology and Education, 2019
Kit-lun Yick, Annie Yu, Pui-ling Li
The results of the subjective sensations also proved that the leather shoes cause the feet to feel the greatest amount of heat and moisture during the different activities which is in agreement with the results of the thermal and humidity values recorded. Thus, feelings of heat and moisture affect the wear comfort of shoes. The results indicated that the elderly group has a higher perceived comfort of the shoe prototypes in comparison to the youth group. The youth group is more sensitive to foot moisture than the elderly group. The results are in agreement with those of a previous study on somesthetic sensitivity (Kenshalo, 1986) in which elderly people show reduced feet sensation. The degenerative loss of sensation of heat, moisture and discomfort of the feet could mean that the elderly are unaware that they are wearing a pair of shoes that are not very air permeable and cannot transfer heat well for a long period of time. This may provide the environment for the growth of bacteria and fungi which not only lead to foot odour but also foot diseases. Therefore, it is recommended that footwear for the elderly have higher air permeability and moisture and heat transfer.